The present invention relates to a rubber composition for an automobile tire and a pneumatic tire using the same.
In order to reduce rolling resistance of a tire, a tire can be made lightweight. The conventional method for obtaining a lightweight tire is the method of reducing the amount of rubber that forms the tire. However, durability of a tire is decreased by this method. Because a small amount of rubber is used, stiffness of the tire and steering stability tend to decrease. Also, when the amount of the filler in a rubber composition is reduced, rolling resistance can be reduced but reinforcement properties of the rubber decrease.
It is conventionally known that wet skid performance and braking performance are improved, when a polymer such as polyethylene is compounded to the rubber component (see JP-A-2001-233994, Japanese Patent No. 3021801, JP-A-9-40809). Also, destruction resistance of the rubber can be improved and low heat generation can be obtained by adding polyethylene (see JP-A-9-241433).
However, in these methods, the kneading temperature of the rubber composition is high and exceeds the melting point of polyethylene. As a result, dispersion of the compounded polyethylene is insufficient. Consequently, steering stability is insufficient and a lightweight tire cannot be prepared. In addition, polyethylene powder is poor in adhesion with diene rubber and is known to easily become the destruction point.